The present invention relates to a printhead for a thermal ink jet printer, and more particularly, to a thermal ink jet printer printhead with a drop ejector that uses a short plug at the front edge of a forward extended pit in the thick photopolymer layer which in combination with an orientation dependent etched (ODE) channel forms an improved nozzle therein.
In thermal ink jet printing, droplets of ink are selectively ejected from a plurality of drop ejectors in a printhead. The ejectors are operated in accordance with digital instructions to create a desired image on a print sheet moving past the printhead. The printhead may move back and forth relative to the sheet in a typewriter fashion, or the linear array may be of a size extending across the entire width of a sheet, to place the image on a sheet in a single pass.
The ejectors typically comprise capillary channels, or other ink passageways, which are connected to one or more common ink supply manifolds. Ink is retained within each channel until, in response to an appropriate digital signal, the ink in the channel is rapidly heated by a heating element disposed on a surface within the channel. This rapid vaporization of the ink adjacent the channel creates a bubble which causes a quantity of liquid ink to be ejected through an opening associated with the channel to the print sheet. The process of rapid vaporization creating a bubble is generally known as xe2x80x9cnucleation.xe2x80x9d One patent showing the general configuration of a typical ink jet printhead is U.S. Pat. No. 4,774,530, assigned to the assignee in the present application and herein incorporated by reference in its entirety for its teaching.
It would be desirable to implement a ink jet printhead which allows usage of a greater variety of inks including viscous inks and to also improve the latency of the ink/printhead combination. This would be desirable so as to open up ink property latitudes so as to allow xe2x80x9cno-compromisexe2x80x9d inks and to reduce the drop volume of thermal ink jet drop ejectors. However, given the need for a heater element and the limited volume amount of ink in the channel, it is only a short matter of time before the ink is dried out in the channel. The amount of time before such drying problems become exhibited is referred to as latency. The longer the latency time for a given head design and ink combination the better. It also follows that improving latency for a given head design will also open up the range of inks which can then be employed by that printhead.
Therefore, as discussed above, there exists a need for a design arrangement which will solve the problem of improving latency in thermal ink jet heads and providing a greater latitude in, and variety of, inks. Thus, it would be desirable to solve this and other deficiencies and disadvantages with an improved ink jet printhead apparatus.
The present invention relates to a thermal ink jet printhead comprising at least one ejector. The ejector comprises an ink channel, and a reservoir situated within the ink channel.
More particularly, the present invention relates to an improved ink jet printhead apparatus, comprising an ink supply manifold supplying ink to one end of an ink channel having a front face. The apparatus further comprises a heater situated in the ink channel, and a reservoir situated in the ink channel between the heater and the front face.
In particular, the present invention relates to a thermal ink jet printhead comprising at least one ejector with a front face, the ejector comprising a structure defining a channel for passage of ink and a heating element within the channel. The heating element is provided in a substantially rectangular heater pit, the heater pit being provided in a layer of material having a thickness and a front edge associated therewith, the front edge to the front face of the ejector defining a hillock.